The present invention relates generally to wastewater treatment. More particularly, the present invention relates to active treatment systems and methods, which effectively and rapidly remove contaminants from wastewater after anaerobic digestion.
Conventional wastewater treatment begins with pretreatment of wastewater, which is carried out in different stages. In an initial stage, wastewater undergoes hydrolysis to convert particulate matter to soluble compounds. These soluble compounds are degraded in a next stage. By way of example, fermentation degrades sugars and fatty acids present in wastewater to produce acetate, hydrogen, and oxygen. Ultimately the degraded compounds are converted to methane gas by typically using methanogenic organisms.
After pretreatment concludes, certain conventional methods may rely on passive techniques, which rely upon nothing more than gravity, to remove suspended solids from wastewater. Typically, a primary sedimentation vault, large enough to store 30 million gallons of water, is employed to carry out sedimentation. Sedimentation is a slow process where relatively heavy solids in wastewater are allowed to settle, such that they sink to the bottom of the vault and produce a discrete solid phase containing heavy solids and a discrete liquid or water phase. As a result, these type solids easily separate from the liquid phase of wastewater.
After heavy solids are removed, wastewater is transported into another large tank to remove organic matter. In this large tank, microorganisms adhere to the thick walls and bottom layer of the tank and thrive under appropriate light, temperature, and surface area in the tank. These microorganisms grow in large enough numbers and consume most of the oxygen and food (i.e., organic matter) present in wastewater. In the absence of conditions necessary to sustain, microorganisms eventually die, leaving behind wastewater that is enriched with nitrogen and phosphorous. Conventional methods discharge this wastewater to the soil, ponds, or tanks depending on the amount of other remaining contaminants.
Unfortunately, conventional wastewater treatment suffers from several drawbacks. For example, not only is the reliance on sedimentation for removal of solids a long and drawn out process, but it is also very expensive. Specifically, infrastructure, such as a large tank, pipes, and pumps, represents significant capital costs.
As another example, the process of removing organic matter, like the process of solid removal, is also passive and expensive as it is carried out over long periods of time in a large tank. As yet another example, conventional treatment methods do not offer provisions for effective removal of dead microorganisms and residual nitrogen and phosphorous from wastewater. Although processes like reverse osmosis or ion exchange are known to remove nitrogen and phosphorous, they are not deemed commercially viable and are therefore not integrated into conventional wastewater treatment methods.
The above-mentioned drawbacks also apply to anaerobic digestion, an important step in treatment of wastewater. Conventional wastewater treatment does not provide for active treatment of wastewater enriched with organic material that results from anaerobic digestion. Anaerobic digestion is a simple process that can greatly reduce the amount of organic matter that might otherwise be destined to be landfilled or burnt in an incinerator. Almost any organic material can be processed with anaerobic digestion, including biodegradable waste materials such as waste paper, grass clippings, leftover food, sewage, and animal waste.
What is therefore needed are systems and methods of wastewater treatment that more effectively and rapidly treat wastewater using anaerobic digestion as an initial step.